Habitat

Atheris squamigera occurs primarily in tropical forests and areas with dense vegetation where small rodents and other prey animals are abundant. This species is most commonly found at elevations ranging from 100 to 400 m in elevation. The climate of the Takamanda Forest Reserve, Cameroon, where this species is particularly abundant, alternates between rainy (April to November) and dry seasons. Rainfall in the Reserve varies from 1500 mm to 10,000 mm per year. In other forest habitats, such as the Guinean Forest in West Africa, A. squamigera occurs most often at lower elevations, which tends to support greater vegetation densities. In general, A. squamigera resides in moist, terrestrial, and arboreal habitats throughout its geographic range. (Chifundera, 1990; Corniskey, et al., 2003; Cundall, 2009)

Physical Description

Atheris squamigera has a compressed body, with scales that are strongly keeled. The dorsal surface of the head is covered with small keeled scales, one of its most distinct features. Typical coloration for is yellowish-green on the dorsum and venter, helping to camouflage it in its natural habitat. Females tend to be slightly larger than males, reaching an average length of 71.2 cm. The average recorded size for males is 65.7 cm. The head is typically larger than their neck, and is triangular. Nasal orientation is lateral, and the openings are partly divided. The snout has a roundish tip and is reltively short. Compared with most other snake species, A. squamigera also has relatively large eyes. It has long, tubular, hollow fangs, which are supplied with venom by a gland located on the upper jaw, between the eyes and mouth. These retractable fangs are connected to a bone that can shift posteriorly within the upper jaw to house the fangs. (Branch and Bayliss, 2009; Chifundera, 1990; Corniskey, et al., 2003; Cundall, 2009; Ota and Hidida, 1987)

Development

After fertilization, Atheris squamigera gives birth to live young (ovoviviparous). Growth is indeterminate, but slows as the snake matures. Juveniles are born venomous and are responsible for capturing their own food. Young snakes can be recognized by the unique coloration of their scales. In addition, the end of their tail is distinctly different and is used as a lure to attract small prey. Time to maturity has not been documented. As individuals age, the coloration of their scales becomes more uniform and may change completely in some cases. (Paukstis and Fredric, 1991)

Reproduction

Although the specific mating system of Atheris squamigera is currently unknown, vipers are typically seasonally monogamous. During courtship, male and female vipers face one another, followed by head and body gestures, which allow for mounting. For example, males often approach their mate while swaying their head side to side in order to engage a female. (Antonio, 1980; Minakami, 1979)

Atheris squamigera reproduces once yearly, typically during the wet season (May to August). Mating occurs most often at night cycle, between 6 pm to 2 am. Once the eggs are fertilized, gestation lasts for 2 months. On average, 7 to 9 offspring are produced. Females reach reproductive maturity 42 months after birth. Males are capable of reproduction much earlier, typically after 24 months. (Luiselli, et al., 2000; Shine, 1980)

Lifespan/Longevity

Average lifespan for green bush vipers has not been documented. Most vipers live 10 to 20 years in the wild. It has been suggested that captive vipers may live longer because risk factors such as predation, disease, and diet are controlled. (Minakami, 1979)

Behavior

Atheris squamigera is nocturnal and like other vipers, is an ambush predator. As such, it spends a large amount of time laying in wait for potential prey to enter its immediate environment. Once in range, A. squamigera strikes very rapidly, with speeds recorded in milliseconds. It spends large amounts of time in one place due to this predatory behavior. Except during mating periods, A. squamigera is a solitary species. (Chifundera, 1990; Cundall, 2009; Freiria, et al., 2006)

Home Range

There is no information available regarding the average home range size of Atheris squamigera.

Communication and Perception

Atheris squamigera uses primarily vision for communication and perception, but also makes use of tactile and olfactory senses. When threatened, it extends its body and raises the anterior portion of its body into the air, settling into a striking position. Posturing is used to ward of predators and during intrasexual competition for mates. During male-male competition, the individual that makes himself appear larger is most often dominant. Communication between sexes is done primarily for reproduction. In order to attract potential mates, males perform a number of different motions, including tail waving, rubbing, biting, and rhythmic body motions. Atheris squamigera lacks the heat-sensing pit organs present in many other viper species. Instead, they rely on visual, tactile, and olfactory senses to detect and capture prey. (Akani, 2000; Carpenter, 1977)

Food Habits

Atheris squamigera is carnivorous. It does most of its hunting at night and is an ambush predator. It feeds mainly on small, nocturnal mammals such as shrews and rodents. Less commonly, it feeds on birds and small reptiles. Juveniles feed on reptiles more often than their adult counterparts. Like other vipers, A. squamigera adults often prey on adolescent snakes of their own species. The venom of A. squamigera is lethal and is used to subdue and kill prey prior to ingestion. In humans, the bite of A. squamigera often causes fever, hemorrhaging, and death. (Akani, 2000; Freiria, et al., 2006; Mueller, 1998)

Predation

Atheris squamigera has few predators. The most commonly noted predators are other snakes, including conspecifics. Humans living near A. squamigera habitat sometime capture it for food, but typically only when it threatens fishing or agricultural activities. (Chifundera, 1990; Corniskey, et al., 2003)

To avoid predation, green bush vipers rely on the same mechanisms used for hunting. Their camouflaged scale patterns allow them to blend in with the surrounding environment. This coloration serves a two-fold purpose, allowing the viper to strike and surprise potential prey, and go unnoticed by potential predators. This ambush-based hiding and hunting behavior allows the snake to sometimes hide rather than engaging in defensive or aggressive behavior. The bright coloration also serves as a warning of the snake's venomous nature to potentially threatening animals. (Chifundera, 1990; Corniskey, et al., 2003)

Economic Importance for Humans: Positive

Many vipers, including Atheris squamigera are farmed for their venom, a process is known as "milking". The venom is used to produce antivenom and for medical and biological uses. Although it is not hunted as a primary food source, it is occasionally captured in fishing nets as by-catch and thus sometimes used as food source. (Chifundera, 1990; Corniskey, et al., 2003; Cundall, 2009)

Economic Importance for Humans: Negative

Green bush vipers are venomous, and as such pose a potential threat to humans. Many unprovoked attacks occur during agricultural activities, as this species is an ambush predator and lies in wait for potential prey. (Chifundera, 1990; Raab and Fitzal, 2005)

Contributors

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

acoustic

uses sound to communicate

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.